Molecular mechanisms of autophagosome biogenesis

摘要 被称为自噬的分解代谢过程对于维持细胞健康和清除细胞是必不可少的 细胞毒素，如异常的大分子、受损的细胞器和入侵细菌。的标志 自噬是被称为自噬小体的双膜小泡的从头形成。该过程开始 通过在内质网(ER)附近组装前体膜噬菌体，随后 通过它在细胞质的非选择性部分或所选的 细胞毒素。在扩张过程中，噬菌体的边缘仍然与内质网相关，并在最后 瞬间，边缘合并，导致杯子关闭，从而产生完整的 自噬小体。自噬对细胞动态平衡的贡献取决于这样一个事实 噬菌体可以吞噬降解底物。吞噬动物要完成这项非凡的任务，它必须 扩张。我们和其他人已经朝着理解心力衰竭的分子机制的目标取得了进展 通过确定ATG2的功能来扩大吞噬载体，ATG2是自噬中最大的蛋白质- 相关蛋白质。我们已经在人类ATG2A上进行了研究，并证明了这种蛋白质是一种杆状蛋白质 能在膜之间转移脂类的膜系绳。我们目前的工作模式是ATG2 通过拴住内质网，将脂类从内质网输送到吞噬体内。然后，输送的脂类将提供 因为构建块构建在底物周围的噬菌体。这项新提案旨在以此为基础 对这一神秘的过程进行建模，并获得更多机械性的见解。在目标1中，我们将扩展我们的研究 ATG2以确定其结构。目的是解释ATG2是如何在膜之间运输脂质的。在……里面 目的2，我们将重点研究ATG9，它是自噬的完整膜蛋白，被称为ATG2 互动演员。通过结构和生物化学特征，我们的目的是阐明这一功能 蛋白质，并获得对吞噬细胞扩张的新见解。在目标3中，我们将描述相互作用 在ATG2和ATG9之间。目标是确定这两种蛋白质是如何相互作用的 结构水平，并探讨ATG2介导的脂质转移及相互作用的意义 吞噬细胞的膨胀。这些研究的结果将从纵向上促进我们对 分子水平上的自噬生物发生。

Abstract The catabolic process known as autophagy is essential for the maintenance of cellular health and the removal of cytotoxins, such as aberrant macromolecules, damaged organelles, and invasive bacteria. The hallmark of autophagy is de novo formation of the double-membrane vesicle called autophagosome. The process begins with assembling the precursor membrane phagophore adjacent to the endoplasmic reticulum (ER), followed by its expansion into a cup-like shape around a non-selective portion of the cytoplasm or a selected cytotoxin. During the expansion, the edges of the phagophore remain associated with the ER and at the last moment, the edges merge, resulting in the closure of the cup, thereby producing a complete autophagosome. The contribution to cellular homeostasis by autophagy hinges on the fact that the phagophore can engulf degradation substrates. For the phagophore to achieve this remarkable task, it must expand. We and others have made progress toward the goal of understanding the molecular mechanism of phagophore expansion by determining the function of ATG2, the largest protein in the group of autophagy- related proteins. We have worked on human ATG2A and demonstrated that this protein is a rod-shaped membrane tether that can transfer lipids between membranes. Our current working model is that ATG2 transports lipids from the ER to the phagophore by tethering them. The transported lipids would then serve as the building blocks the phagophore built around the substrates. This new proposal aims to build on this model and gain further mechanistic insights into this enigmatic process. In Aim 1, we will extend our study of ATG2 to determine its structure. The goal is to explain how ATG2 transports lipids between membranes. In Aim 2, we will focus on ATG9, the integral membrane protein of autophagy that has been known as an ATG2 interactor. Through structural and biochemical characterizations, we aim to elucidate the function of this protein and gain new insights into phagophore expansion. In Aim 3, we will characterize the interaction between ATG2 and ATG9. The goal is to determine how these two proteins interact with each other at the structural level and explore the significance of the interaction for ATG2-mediated lipid transfer and phagophore expansion. Results from these studies will vertically advance our understanding of autophagosome biogenesis at the molecular level.